The present invention relates to semiconductor integrated circuit devices, and more particularly to techniques which are effective when applied to a semiconductor integrated circuit device having a conductor film on a substrate.
A semiconductor integrated circuit device which the inventor is developing, is so constructed that a mother chip on which a plurality of semiconductor chips are mounted is encapsulated by a base board and a sealing cap. This semiconductor integrated circuit device is used as, for example, a RAM module in which the plurality of semiconductor chips each having a built-in RAM (Random Access Memory) are mounted on the mother chip.
Each of the semiconductor chips is mounted on the mother chip by so-called face-down bonding (Controlled Collapse Bonding) wherein bump electrodes are interposed. One end side of the bump electrode is connected to the external terminal (bonding pad) of the semiconductor chip, while the other end side thereof is connected to the terminal of the mother chip. The bump electrodes are formed of a solder which is evaporated by the use of a metal mask.
Incidentally, the semiconductor integrated circuit device of this type is described in, for example, "Nikkei Electronics" dated Sept. 24, 1984, pp. 265-294, published by Nikkei McGraw-Hill Inc. In addition, the formation of bump electrodes by the use of a metal mask is described in "VSLI TECHNOLOGY," pp. 564-570, published by McGraw-Hill Inc.
Upon studying the subject that the bump electrodes for connecting the semiconductor chip and the mother chip are formed by a lift-off technique, the inventor is making basic researches thereon. The bump electrodes formed by the lift-off technique can be finished up more precisely as compared with the bump electrodes formed using the metal mask. In other words, the lift-off technique has the feature that the bump electrodes are formed at a higher density, so the density of integration of the semiconductor integrated circuit device can be raised.
The manufacturing technique which the inventor is developing, is as follows:
First, the whole front surface of the mother chip including the terminals thereof is coated with a photoresist film. After the photoresist film has been baked, its parts on the terminals of the mother chip are removed by development so as to form openings.
Subsequently, the solder is evaporated on the photoresist film and o the terminals lying inside the openings.
Next, the photoresist film is stripped off by a peeling solution so as to leave the solder inside the openings, thereby to form the bump electrodes and to remove the solder lying on the photoresist film. Thus, the bump electrodes are formed by the lift-off technique employing the photoresist film.